Semiconductor light emitting device in which near-edge portion is filled with doped regrowth layer, and dopant to regrowth layer is diffused into near-edge region of active layer

ABSTRACT

In a process for producing a semiconductor light emitting device, first, a lamination including an active zone, cladding layers, and a current confinement layer is formed. Then, a near-edge portion of the lamination having a stripe width is removed so as to produce a first space, and a second near-edge portion located under the first space and a stripe portion of the lamination being located inside the first space and having the stripe width are concurrently removed so that a second space is produced, and cross sections of the active layer and the current confinement layer are exposed in the second space. Finally, the first and second spaces are filled with a regrowth layer so that a dopant to the regrowth layer is diffused into a near-edge region of the remaining portion of the active layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light emitting devicehaving an end-facet window structure which prevents carrierrecombination at a light-exit end facet. The present invention alsorelates to a process for producing such a semiconductor light emittingdevice.

2. Description of the Related Art

In conventional semiconductor light emitting devices, when opticaloutput power is increased, currents generated by optical absorption invicinities of end facets generate heat, i.e., raise the temperature atthe end facets. In addition, the raised temperature reduces thesemiconductor bandgaps at the end facets, and therefore the opticalabsorption is further enhanced. That is, a vicious cycle is formed, andthe end facet is damaged. This damage is the so-called catastrophicoptical mirror damage (COMD). Thus, the maximum optical output power islimited due to the COMD. In order to overcome the above problem, varioustechniques have been proposed for the window structures which preventthe light absorption in the vicinities of end facets by increasing thesemiconductor bandgaps in the vicinities of the end facets.

For example, Japanese Unexamined Patent Publication No. 2000-31596discloses a semiconductor laser device and a process for producing asemiconductor laser device. In the process, a window structure isrealized by removing a portion of an upper cladding layer in a vicinityof light-exit end facet to a depth near a quantum-well active layer byetching, and forming a regrowth layer doped with the same dopant as thatof an upper cladding layer so that the dopant diffuses into thequantum-well active layer, and crystal mixture occurs in thequantum-well active layer.

Since, in the above process, the dopant is diffused into thequantum-well active layer through the cladding layer and an opticalwaveguide layer during the formation of the regrowth layer, thediffusion depth of the dopant and the degree of the crystal mixture varydue to irregularity of thermal diffusion occurring during the formationof the regrowth layer, and therefore the window structure has poorreproducibility. Thus, it is difficult to produce, at a high yield rate,the above semiconductor laser device so that the semiconductor laserdevice is reliable in a high output power operation. In addition, in theabove process, three semiconductor-layer growing steps and two dryetching steps are required to be performed until a semiconductor laserchip is completed. That is, the manufacturing process is complicated,and the manufacturing cost is high.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor lightemitting device which is reliable in a high output power operation.

Another object of the present invention is to provide a process whichcan produce a semiconductor light emitting device being reliable in ahigh output power operation, through a small number of manufacturingsteps with high reproducibility.

(1) According to the first aspect of the present invention, there isprovided a semiconductor light emitting device comprising: a layeredstructure and a regrowth layer formed over the layered structure. Thelayered structure includes a lower cladding layer of a first conductivetype, an active zone including an active layer, an upper cladding layerof a second conductive type, and a current confinement layer, which areformed on a substrate in this order. In the layered structure, a groovehaving a depth corresponding to a bottom of said current confinementlayer or a lower elevation is formed for realizing a current injectionwindow, and at least one space is formed between at least one near-edgeregion of the active zone and at least one end facet. The regrowth layeris doped with a dopant which makes the regrowth layer the secondconductive type, and formed over the layered structure so that thegroove and the at least one space in the layered structure are filledwith the regrowth layer, and the dopant is diffused into at least onenear-edge region of the active layer.

The first conductive type is different in the polarity of carriers fromthe second conductive type. That is, when the first conductive type isan n type, and the second conductive type is a p type.

In the semiconductor light emitting device according to the first aspectof the present invention, at least one space is produced between atleast one end facet and the at least one near-edge region of the activezone, and is filled with the regrowth layer so that the dopant withwhich the regrowth layer is doped is diffused into the at least onenear-edge region of the active layer. Therefore, crystal mixture occursin the at least one near-edge region of the active layer, and the energygap in the at least one near-edge region of the active layer isincreased. Thus, the light absorption in the at least one near-edgeregion of the active layer is reduced. In particular, even when theoutput power is increased, and the temperature rises, the lightabsorption in the at least one near-edge region of the active layer canbe reduced. Therefore, it is possible to obtain a semiconductor lightemitting device which is reliable even in a high output power operation.

Preferably, the semiconductor light emitting device according to thefirst aspect of the present invention may also have one or any possiblecombination of the following additional features (i) to (iv).

(i) A first partial thickness of the layered structure corresponding tothe depth of the groove has such composition that the first partialthickness of the layered structure can be etched off by wet etchingconcurrently with the active layer and a second partial thickness of thelayered structure above the active layer.

When the semiconductor light emitting device according to the firstaspect of the present invention has the above additional feature (i),and the at least one space between the at least one end facet and the atleast one near-edge region of the active layer is produced by forming alamination of the lower cladding layer, the active zone, the uppercladding layer, and the current confinement layer on the substrate, andetching off at least one near-edge portion of the lamination having adepth corresponding to the bottom of the active layer or a lowerelevation, and the groove is produced by etching off a stripe portion ofthe lamination being located inside the at least one space and havingthe depth corresponding to the bottom of the current confinement layeror a lower elevation, the etching-off operations for producing the atleast one space and the groove can be performed concurrently by anidentical lithography process or a self alignment process. Therefore,the number of manufacturing steps can be reduced.

(ii) The substrate is made of GaAs, the lower cladding layer and theupper cladding layer are made of InGaP or AlGaAs, the active layer ismade of In_(x)Ga_(1−x)As_(1−y)P_(y) (0≦x≦0.4, 0≦y≦0.1), and the currentconfinement layer is made of InGaP of the first conductive type. Theactive zone further includes a lower optical waveguide layer made ofIn_(x3)Ga_(1−x3)As_(1−y3)P_(y3) (x3=0.49y3, 0≦x3≦0.3) of an intrinsictype or the first conductive type and formed under the active layer, andan upper optical waveguide layer made of In_(x3)Ga_(1−x3)As_(1−y3)P_(y3)(x3=0.49y3, 0≦x3≦0.3) of an intrinsic type or the second conductive typeand formed above the active layer. The layered structure furtherincludes a buffer layer made of GaAs and formed between the substrateand the lower cladding layer, and an etching stop layer made of GaAs andformed under the current confinement layer. The lower optical waveguidelayer may be arranged immediately under the active layer, and the upperoptical waveguide layer may be arranged immediately above the activelayer.

In addition, the InGaP material is a semiconductor material containingat least indium, gallium, and phosphor as components, and the AlGaAsmaterial is a semiconductor material containing at least aluminum,gallium, and arsenic as components. Further, preferably, thecompositions of the lower and upper cladding layers are such that thelower and upper cladding layers lattice-match with the GaAs substrate.In particular, it is preferable that the composition of the InGaPmaterial is In_(0.49)Ga_(0.51)P, and the composition of the AlGaAsmaterial is Al_(0.5)Ga_(0.5)As.

(iii) The at least one space has an approximately identical width with awidth of the groove, and is located adjacent to the groove.

(iv) The second conductive type is a p type, to and the dopant is Zn. Inthis case, the bandgap in the vicinity of the end facet can besatisfactorily increased. Therefore, the light absorption in thevicinity of the end facet can be reduced, and high reliability can bemaintained even in a high output power operation.

(2) According to the second aspect of the present invention, there isprovided a process for producing a semiconductor light emitting device,comprising the steps of: (a) forming a substrate; (b) forming above thesubstrate a lower cladding layer of a first conductive type; (c) formingabove the lower cladding layer an active zone including an active layer;(d) forming above the active zone an upper cladding layer of a secondconductive type; (e) forming a current confinement layer above the uppercladding layer, and obtaining a lamination of the lower cladding layer,the active layer, the upper cladding layer, and the current confinementlayer; (f) removing at least one first near-edge portion of thelamination being located near at least one of two opposite end facetsand having a first depth and a width corresponding to a stripe width soas to produce at least one first space, by etching the lamination with afirst mask which has an opening corresponding to the first near-edgeportion; (g) removing at least one second near-edge portion of thelamination being located near the at least one of the two opposite endfacets and having the stripe width and a second depth corresponding tothe bottom of the active layer or a lower elevation, and a stripeportion of the lamination being located inside the at least one firstspace and having the stripe width and a third depth corresponding to thebottom of the current confinement layer or a lower elevation, so as toproduce a second space, by etching the lamination with a second maskwhich has a stripe opening having a width corresponding to the stripewidth and extending from one to the other of the two opposite endfacets; and (h) forming a regrowth layer so as to fill the at least onefirst space and the second space.

The above first width corresponds to a width of a current injectionregion.

According to the second aspect of the present invention, in the step(f), a first partial thickness of the near-edge portion of thelamination (i.e., the at least one first near-edge portion of thelamination) having the width corresponding to the stripe width isremoved by etching. Thereafter, in the step (g), a second partialthickness of the near-edge portion of the lamination (i.e., the at leastone second near-edge portion of the lamination) and having the stripewidth is removed by using a mask which has an opening having the stripewidth so that at least the full thickness of a cross section of theactive layer is exposed, and at the same time, a stripe portion of thelamination being located inside the at least one first space (producedin step (f)) and having the stripe width is removed by using the samemask so that at least the full thickness of a cross section of thecurrent confinement layer is exposed. Thus, the formation of the stripegroove for the internal stripe structure and the removal of thenear-edge portion of the active zone can be concurrently achieved byusing the same mask. In other words, the conventional manufacturingprocess of forming the end-facet window structure and the conventionalmanufacturing process of forming the internal stripe structure can besubstituted by a common step of lithography and etching and a commonstep of forming a regrowth layer, although each of the aboveconventional manufacturing processes includes a step of forming a stepof lithography and etching and a step of forming a regrowth layer. Thus,the total manufacturing process can be simplified by the second aspectof the present invention.

In addition, since the at least one near-edge space for the end-facetwindow structure and the groove for the internal stripe structure areformed by one lithography process, the at least one near-edge spaceproduced by the removal of the at least one near-edge portion is wellaligned with the stripe groove without any provision for realizing thealignment, and the reproducibility in the formation of the end-facetwindow structure and the groove for the internal stripe structure ishigh.

Further, since the near-edge portion of the active zone is removed, andis thereafter filled with the regrowth layer, the dopant of the secondconductive type in the regrowth layer can be diffused into the at leastone near-edge portion of the active layer with high reliability andreproducibility during the formation of the regrowth layer.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a first stage in a process forproducing a semiconductor laser device as an embodiment of the presentinvention.

FIG. 1B is a perspective view of a second stage in the process forproducing the semiconductor laser device as the embodiment of thepresent invention.

FIG. 1C is a perspective view of a third stage in the process forproducing the semiconductor laser device as the embodiment of thepresent invention.

FIG. 1D is a perspective view of a fourth stage in the process forproducing the semiconductor laser device as the embodiment of thepresent invention.

FIG. 2A is a perspective view of a fifth stage in a process forproducing a semiconductor laser device as the embodiment of the presentinvention.

FIG. 2B is a perspective view of a sixth stage in the process forproducing the semiconductor laser device as the embodiment of thepresent invention.

FIG. 2C is a cross-sectional view of a final stage in the process forproducing the semiconductor laser device as the embodiment of thepresent invention.

FIG. 3 is perspective view of a laser array bar including a plurality ofsemiconductor laser elements in the embodiment of the present invention.

FIG. 4 is diagram illustrating a solid-state laser apparatus using as anexcitation light source the semiconductor laser device as the embodimentof the present invention.

FIG. 5 is diagram illustrating another solid-state laser apparatus usingas an excitation light source the semiconductor laser device as theembodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention are explained in detail below withreference to drawings.

Embodiment of Semiconductor Laser Device

A process for producing a semiconductor laser device as an embodiment ofthe present invention is explained below. FIGS. 1A to 2B are perspectiveviews of representative stages in a process for producing thesemiconductor laser device as the embodiment of the present invention,and FIG. 2C is a cross-sectional view of the final stage in the processfor producing the semiconductor laser device. Although, in practice, aplurality of semiconductor laser devices are concurrently manufacturedon a wafer of a substrate, and arranged side by side, a construction ina stage corresponding to only one semiconductor laser device isindicated in each of FIGS. 1A to 2C for the sake of simplicity ofillustration and better understanding.

First, as illustrated in FIG. 1A, an n-type GaAs substrate 12, an n-typeIn_(0.49)Ga_(0.51)P lower cladding layer 13, an n-type or i-typeIn_(x3)Ga_(1−x3)As_(1−y3)P_(y3) lower optical waveguide layer 14(x3=0.49y3, 0≦x3≦0.3), an In_(x)Ga_(1−x)As_(1−y)P_(y) quantum-wellactive layer 15 (0≦x≦0.4, 0≦y≦0.1), a p-type or i-typeIn_(x3)Ga_(1−x3)As_(1−y3)P_(y3) upper optical waveguide layer 16(x3=0.49y3, 0≦x3≦0.3), a p-type In_(0.49)Ga_(0.51)P first upper claddinglayer 17, and a GaAs etching stop layer 18 are formed on a (100) face ofan n-type GaAs substrate 11 by organometallic vapor phase epitaxy, wherethe n-type or i-type In_(x3)Ga_(1−x3)As_(1−y3)P_(y3) lower opticalwaveguide layer 14 (x3=0.49y3, 0≦x3≦0.3), theIn_(x)Ga_(1−x)As_(1−y)P_(y) quantum-well active layer 15 (0≦x≦0.4,0≦y≦0.1), and the p-type or i-type In_(x3)Ga_(1−x3)As_(1−y3)P_(y3) upperoptical waveguide layer 16 (x3=0.49y3, 0≦x3≦0.3) constitute an SCH(separate confinement heterostructure) layer as an active zone. Further,an n-type In_(0.49)Ga_(0.51)P current confinement layer 19 and a GaAscap layer 20 are formed on the above layers.

Next, a resist (not shown) is applied to the layers formed as above, andpredetermined regions are removed by conventional lithography so as toform openings 21 as illustrated in FIG. 1B. The openings 21 have a width(W) of 3 micrometers in the direction which is perpendicular to anorientation flat of the wafer of the n-type GaAs substrate 11 andparallel to cleavage surfaces of the semiconductor laser device, and alength00 (L) of about 15 micrometers in the direction which is parallelto the orientation flat and perpendicular to the cleavage surfaces.Since, in practice, a plurality of semiconductor laser devices areconcurrently manufactured on the wafer of the n-type GaAs substrate 11,and arranged side by side, openings 21 each have a width (W) of 3micrometers in the direction which is perpendicular to the orientationflat and parallel to the cleavage surfaces and a length of about 30micrometers in the direction which is parallel to the orientation flatand perpendicular to the cleavage surfaces are formed on the wafer.Then, the GaAs cap layer 20 is etched off with a tartaric acid etchant,the resist is removed, and the n-type In0.49Ga0.51P current confinementlayer 19 is etched off with a hydrochloric acid etchant.

Thereafter, another resist 22 is applied to the layers formed as above,and a stripe region having a width of 3 micrometers and being directedin the direction parallel to the orientation flat is removed byconventional lithography so as to form a stripe groove which overlapsthe above openings 21 as illustrated in FIG. 1C. Then, a stripe portionof the GaAs cap layer 20 exposed at the bottom of the stripe groove andportions of the GaAs etching stop layer 18 exposed by the formation ofthe above openings 21 are etched off with a tartaric acid etchant, andthe resist 22 is removed.

Next, as illustrated in FIG. 1D, portions of the p-type In0.49Ga0.51Pfirst upper cladding layer 17 and a stripe portion of the n-typeIn0.49Ga0.51P current confinement layer 19, which are exposed by theetching of the above portions of the GaAs cap layer 20 and the GaAsetching stop layer 18, are also etched off with a hydrochloric acidetchant. Then, the remaining portions of the GaAs cap layer 20 and astripe portion of the GaAs etching stop layer 18 exposed by the etchingof the above stripe portion of the n-type In0.49Ga0.51P currentconfinement layer 19 are etched off with a tartaric acid etchant. At thesame time, portions of the p-type or i-type Inx3Ga1−x3As1−y3Py3 upperoptical waveguide layer 16 (x3=0.49y3, 0≦x3≦0.3), the InxGa1−xAs1−yPyquantum-well active layer 15 (0≦x≦0.4, 0≦y≦0.1), and the n-type ori-type Inx3Ga1−x3As1−y3Py3 lower optical waveguide layer 14 (x3=0.49y3,0≦x3≦0.3), which are located under the above openings 21, i.e., portionsof the active zone under the openings 21, are also etched off.

Thereafter, as illustrated in FIG. 2A, a p-type (Zn-doped)In_(0.49)Ga_(0.51)P second upper cladding layer 23 and a p-type GaAscontact layer 24 are formed on the layered structure formed as above.Since the In_(0.49)Ga_(0.51)P second upper cladding layer 23 is dopedwith Zn, Zn diffuses from the side surfaces of the openings 21 into theactive layer, causes crystal mixture, and thus window structures areformed.

Next, a p electrode 25 is formed by the lift-off technique on an area ofthe p-type GaAs contact layer 24 so as not to cover the above windowstructures as illustrated in FIG. 2B, and areas of the p-type GaAscontact layer 24 which are not covered by the p electrode 25 are etchedoff with an NH₃:H₂O₂ solution by using the p electrode 25 as a mask.Then, the exposed (opposite) surface of the substrate 11 is polished,and an n electrode 26 is formed on the polished surface of the substrate11.

FIG. 2C is a cross-sectional view of the final stage in the process forproducing the semiconductor laser device as the embodiment of thepresent invention. That is, each semiconductor laser device as theembodiment of the present invention, formed as above, has a crosssection as illustrated in FIG. 2C. In each semiconductor laser device,near-edge portions of the active zone are removed, and are filled withthe p-type (Zn-doped) In_(0.49)Ga_(0.51)P second upper cladding layer23. Thus, the p-type dopant, Zn, is diffused into near-edge regions ofthe remaining portion of the active zone as indicated by hatching inFIG. 2C, and therefore the bandgaps of the active zone are increased.Consequently, it is possible to prevent light absorption in the vicinityof the end facet, and achieve high reliability even in a high outputpower operation.

In the above construction, the thickness of the first upper claddinglayer 17 is such that index guidance in a single fundamental mode isachieved in a waveguide formed in the center of the resonator under thestripe groove even when the output power becomes high.

After the above layered structure is formed on the wafer, the wafer iscleaved at the positions of the end facets into laser array bars 60 asillustrated in FIG. 3. Then, high-reflection coating 61 andlow-reflection coating 62 are laid on the end facets of the laser arraybars 60. Thereafter, the laser array bars 60 are further cleaved intochips. Thus, the semiconductor laser device as the embodiment of thepresent invention is obtained.

Since the active layer has a composition of In_(x)Ga_(1−x)As_(1−y)P_(y),the oscillation wavelengths of the semiconductor laser device as theembodiment of the present invention can be controlled in the range of900 to 1,200 nm.

Although the n-type GaAs substrate is used in the construction of theembodiment of the present invention, instead, a p-type GaAs substratemay be used. When the GaAs substrate is a p-type, the conductivity typesof all of the other layers in the construction of the embodiment shouldbe inverted.

Each layer in the constructions of the embodiment may be formed bymolecular beam epitaxy using solid or gas raw material.

The second upper cladding layer 23 may be made of Al_(0.5)Ga_(0.5)As,instead of In_(0.49)Ga_(0.51)P.

In the semiconductor laser device as the embodiment of the presentinvention, the GaAs etching stop layer 18 and the GaAs cap layer 20 areformed on and under the n-type In_(0.49)Ga_(0.51)P current confinementlayer 19. Therefore, after the near-edge regions of the GaAs cap layer20 and the n-type In_(0.49)Ga_(0.51)P current confinement layer 19 areremoved by using a mask with openings having the same width as thestripe groove, the near-edge regions of the layers from the GaAs etchingstop layer 18 to the n-type or i-type In_(x3)Ga_(1−x3)As_(1−y3)P_(y3)lower optical waveguide layer 14 and the stripe center portions of thelayers from the GaAs cap layer 20 to the GaAs etching stop layer 18 canbe concurrently removed by etching in the stages of FIGS. 1C and 1D byusing the mask having the stripe opening. That is, the end-facet windowstructure and the internal stripe can be concurrently formed, and thusthe manufacturing process can be simplified.

In addition, since the end-facet window structure having the same widthas the internal stripe is automatically formed in the regions adjacentto the internal stripe, the dopant Zn in the p-type In_(0.49)Ga_(0.51)Psecond upper cladding layer 23 can diffuse into near-edge regions of theactive layer with high accuracy, i.e., the end-facet window structurecan be formed with high reproducibility.

Further, since the GaAs cap layer 20 is formed on the n-typeIn_(0.49)Ga_(0.51)P current confinement layer 19, it is possible toprevent production of a metamorphic layer on the InGaP currentconfinement layer, or adherence of dirt to the InGaP current confinementlayer, although the metamorphic change occurs when a resist layer isformed directly on the current confinement layer. In addition, the GaAscap layer 20 can be removed together with the near-edge portions of theGaAs etching stop layer 18. Therefore, even when a metamorphic layer isproduced on the InGaP current confinement layer, or dirt adheres to theInGaP current confinement layer, the metamorphic layer and the dirt canbe removed by the operation of removing the GaAs cap layer 20.

Although the semiconductor laser device as the embodiment oscillates ina fundamental transverse mode, the present invention can also be appliedto a broad-stripe semiconductor laser device having a stripe width of 3micrometers or greater. In this case, it is possible to increasereliability in a further high output power range.

Furthermore, when antireflection coatings, instead of thehigh-reflection coating 61 and the low-reflection to coating 62, arelaid on both the (cleaved) end facets, a semiconductor light emittingdevice in which laser oscillation does not occur can be produced.

First Example of Use

A first example of use of the semiconductor laser device as the aboveembodiment is explained below with reference to FIG. 4, which is adiagram illustrating an outline of a construction of a solid-state laserapparatus which generates a second harmonic. In the example of FIG. 4,the semiconductor laser device as the above embodiment is used as anexcitation light source in the solid-state laser apparatus.

The solid-state laser apparatus of FIG. 4 comprises a semiconductorlaser device 71, a lens 72, a solid-state laser crystal 73, an outputmirror 74, a KNbO₃ nonlinear crystal 75, a coating film 76, a beamsplitter 77, and a light receiving element 78. The semiconductor laserdevice 71 is the semiconductor laser device as the embodiment of thepresent invention, and emits single-mode light as the excitation light.The lens 72 collects the excitation light emitted from the semiconductorlaser device 71. The solid-state laser crystal 73 is excited by thecollected excitation laser light, and emits laser light. The outputmirror 74 is realized by a concave mirror. In addition, the coating film76 is provided on a surface of the solid-state laser crystal 73 on theside of the semiconductor laser device 71. The coating film 76 highlyreflects the oscillation light of the solid-state laser crystal 73, anddoes not reflect the oscillation light of the semiconductor laser device71. Thus, a resonator is realized between the output mirror 74 and thecoating film 76 in the solid-state laser apparatus. Further, the KnbO₃nonlinear crystal 75, which converts the oscillation light of thesolid-state laser crystal 73 into a second harmonic (i.e., generateslaser light having the half wavelength of the oscillation light of thesolid-state laser crystal 73), is arranged in the resonator of thesolid-state laser apparatus. The nonlinear crystal 75 may be made of KTP(KTiOPO₄) or the like, instead of KNbO₃. In addition, the solid-statelaser crystal 73 may be made of Nd:YVO₄ or the like.

The temperature of the semiconductor laser device 71, the solid-statelaser crystal 73, and the nonlinear crystal 75 is controlled by using aPeltier element (not shown). A portion of laser light emitted from thesolid-state laser apparatus is branched off by the beam splitter 77, andled to the light receiving element 78, which detects the intensity ofthe branched-off portion of the laser light. The detected intensity isfed back to the semiconductor laser device 71 so that the semiconductorlaser device 71 is driven under automatic power control (APC), and theintensity of the laser light emitted from the solid-state laserapparatus is maintained constant.

Since the semiconductor laser device as the embodiment of the presentinvention is used in the above solid-state laser apparatus, highreliability is achieved even in a high output power operation.

Second Example of Use

A second example of use of the semiconductor laser device as theembodiment is explained below with reference to FIG. 5, which is adiagram illustrating an outline of a construction of another solid-statelaser apparatus which generates a second harmonic. In the example ofFIG. 5, the semiconductor laser device as the above embodiment is alsoused as an excitation light source in the solid-state laser apparatus.

The laser apparatus of FIG. 5 comprises a Peltier element 80, asemiconductor laser device 81, a waveguide grating 82, a MgO-LNwaveguide SHG (second harmonic generator) 83, a beam splitter 86, and alight receiving element 87. The semiconductor laser device 81 is thesemiconductor laser device as the embodiment of the present invention,and emits single-mode light as the excitation light. The semiconductorlaser device 81, the waveguide grating 82, and the MgO-LN waveguide SHG83 are mounted on the Peltier element 80, and the temperature of thesemiconductor laser device 81, the waveguide grating 82, and the MgO-LNwaveguide SHG 83 are controlled by the Peltier element 80. Inparticular, the waveguide grating 82 is mounted on an identical axiswith that of the semiconductor laser device 81, and independentlycoupled to the semiconductor laser device 81. The waveguide grating 82locks the wavelength of the laser light emitted from the semiconductorlaser device 81. The MgO-LN waveguide SHG 83 is an optical wavelengthconversion element which is produced by forming an optical waveguide anda periodic domain-inverted structure on a substrate made of LiNbO₃ anddoped with MgO. When the MgO-LN waveguide SHG 83 receives thewavelength-locked laser light emitted from the semiconductor laserdevice 81, and the MgO-LN waveguide SHG 83 converts the laser light ofthe semiconductor laser device 81 into a second harmonic (i.e.,generates laser light having the half wavelength of the laser light ofthe semiconductor laser device 81).

Additional Matters

(i) The semiconductor laser device according to the present inventioncan be used as a light source in arrayed semiconductor laserapparatuses, optical integrated circuits, and the like, as well as thesolid-state laser apparatuses as the aforementioned first and secondexamples. Further, the semiconductor laser device according to thepresent invention can be used as a light source in the fields ofhigh-speed information and image processing, communications, lasermeasurement, medicine, printing, and the like.

What is claimed is:
 1. A process for producing a semiconductor lightemitting device, comprising the steps of: (a) forming a substrate; (b)forming above said substrate a lower cladding layer of a firstconductive type; (c) forming above said lower cladding layer an activezone including an active layer; (d) forming above said active zone anupper cladding layer of a second conductive type; (e) forming a currentconfinement layer above said upper cladding layer, and obtaining alamination of the lower cladding layer, the active layer, the uppercladding layer, and the current confinement layer; (f) removing at leastone first near-edge portion of said lamination being located near atleast one of two opposite end facets and having a first depth and awidth approximately equal to a stripe width so as to produce at leastone first space, by etching said lamination with a first mask which hasan opening corresponding to said first near-edge portion; (g)concurrently removing at least one second near-edge portion of saidlamination being located near said at least one of said two opposite endfacets and having said stripe width and a second depth corresponding toa bottom of said active layer or a lower elevation, and a stripe portionof said lamination being located inside said at least one first spaceand having said stripe width and a third depth corresponding to a bottomof said current confinement layer or a lower elevation, so as to producea second space, by etching said lamination with a second mask which hasa stripe opening having a width corresponding to said stripe width andextending from one to the other of the two opposite end facets; and (h)forming a regrowth layer so as to fill said at least one first space andsaid second space.